Before including this post here, I looked around to find an appropriate category, but really found none. If the moderators feel it belongs elsewhere, please feel free to move it.

I've recently rented a storage unit in a building with temperature and humidity control, and had shelving built to maximize the use of the space. At present I have all my works stored vertically on these shelves divided by large pieces of cardboard. My question is whether each painting should be covered in some way, either wrapped in some sort of large sheet or a large plastic bag, or if they are better without individual protection.

Oil paintings are pretty tough. If they're stored in the dark, they may darken somewhat, a change that's reversable when they are returned to normal room lighting.

A painting stored directly in contact with any material (or another painting) poses something of a problem. It's not inconceivable the common cardboards could be reactive in time with bad effects because of their acid content. Practically all plastics are chemically active to some extent, off-gassing volatile elements (e.g., anything you can smell) and containing plasticizing agents that may react or migrate in the presence of other materials that also contain solvents and volatile elements . . . such as paints and varnishes, so plastic sheeting could cause problems when directly in contact with a painting. Much depends on the age of the painting, the type of plastic, and the length of time in contact.

Between bonfires, I store my "backlog" paintings vertically in wooden racks, no contact one with another, or other materials. Museums store paintings in shallow dust-proof cabinets faced with glass under ambient light,, hung separately as on a wall, whether framed or unframed.